Cancers are the commonest cause for death among all of the causes for death, and the therapies currently carried out therefor are mainly surgical treatment in combination with radiotherapy and chemotherapy. In spite of the developments of new surgical methods and discovery of new anti-cancer agents in recent years, treatment results of cancers are not improved very much at present except for some cancers. In recent years, by virtue of development in molecular biology and cancer immunology, cancer antigens recognized by antibodies and cytotoxic T cells which are specifically reactive with cancers, as well as the genes encoding the cancer antigens, were identified, and expectations for therapeutic methods specifically targeting cancer antigens have been raised (Non-patent Literature 1).
In a therapeutic method for cancer, to reduce side effects, it is desired that the peptide, polypeptide or protein recognized as the antigen exist hardly in normal cells and exist specifically in cancer cells. In 1991, Boon et al. in Ludwig Institute in Belgium isolated a human melanoma antigen MAGE 1 recognized by CD8-positive T cells by a cDNA-expression cloning method using an autologous cancer cell line and cancer-reactive T cells (Non-patent Literature 2). Thereafter, the SEREX (serological identifications of antigens by recombinant expression cloning) method, wherein tumor antigens recognized by antibodies produced in the living body of a cancer patient in response to the cancer of the patient himself are identified by application of a gene expression cloning method, was reported (Non-patent Literature 3; Patent Literature 1), and several cancer antigens which are hardly expressed in normal cells while being specifically expressed in cancer cells have been isolated by this method (Non-patent Literatures 4 to 9). Further, using a part thereof as targets, clinical tests for cell therapies using immunocytes specifically reactive with the cancer antigens, and cancer-specific immunotherapies such as those using vaccines containing the cancer antigens have been carried out.
On the other hand, in recent years, various antibody drugs for therapy of cancer have become conspicuous in the world, which drugs target antigen proteins on cancer cells. Since certain levels of pharmacological effects can be obtained with such antibody drugs as cancer-specific therapeutic agents, they are drawing attention, but most of the antigen proteins to be targeted are those also expressed in normal cells, so that, as a result of administration of the antibody, not only cancer cells, but also normal cells expressing the antigen are damaged, resulting in occurrence of side effects, which has been problematic. Thus, it is expected that identification of cancer antigens specifically expressed on the surfaces of cancer cells and employment of antibodies targeting these as drugs will allow therapy with antibody drugs with less side effects.
CD179b is known to be a part of the surrogate light chain of immunoglobulin and expressed on the membrane surfaces of precursor cells of B cells (pre-B cells and pro-B cells). It disappears upon differentiation of B cells and is not expressed in mature B cells. However, CD179b is known to be expressed in leukemia (pre-B cell leukemia) cells produced by cancerization of pre-B cells (Non-patent Literatures 10 and 11). Further, CD179b is known to be expressed also in lymphoma (pre-B cell lymphoma) cells produced by cancerization of pre-B cells, and able to be used as a diagnostic marker for pre-B cell lymphoma (Non-patent Literature 12). However, its specific expression has not been reported for leukemia cells other than pre-B cell leukemia cells, lymphomas other than pre-B cell lymphoma, breast cancer cells and the like. Further, there has been no report suggesting that antibodies against CD179b are useful for therapy and/or prophylaxis of cancer.